1. Field of Invention
The invention relates to a hybrid drive unit and an FR (as abbreviated from “Front-Engine/Rear-Drive”) type automobile having the hybrid drive unit mounted thereon.
2. Description of Related Art
The hybrid drive unit is exemplified by a so-called “two-motor type”, wherein two motors are used, which is mounted on an automobile. In this two-motor type, the output torque of a planetary gear is continuously controlled by distributing the output torque from an engine to a motor (generally called the “generator”) and an output shaft. Also, the output torque of another motor (generally called the “drive motor”) is synthesized, if necessary, with the planetary gear output torque and is outputted to the output shaft.
The two-motor type hybrid drive unit is mounted as an FF (as abbreviated from “Front-Engine/Front-Drive”) type on the automobile. As disclosed in German Patent No. DE 19803160, for example, it is intended to mount the hybrid drive unit on a front engine, rear wheel drive type large-sized automobile. This front engine, rear wheel drive type hybrid drive unit is schematically shown in FIG. 9.
In an automobile 1 having the hybrid drive unit mounted thereon, as shown in FIG. 9, an internal combustion engine 6 such as a gasoline engine is so arranged in the front portion of a body 2, i.e., in the portion between front wheels 3a and 3b with the crank shaft positioned in the longitudinal direction. Moreover, the two-motor type hybrid drive unit 54 is arranged at the back of and adjacent to the engine 6. In the hybrid drive unit 54, a first motor (or generator) 10, a power distributing planetary gear 11 and a second motor (or drive motor) 40 are arranged with the crank shaft generally in the axial direction and are arranged sequentially in the recited order from the engine side. Here, reference numerals 4a and 4b designate the drive shafts of the left and right front wheels 3a and 3b, respectively.
In the hybrid drive unit 54, an input shaft 28 is connected through a damper unit 9 to an output shaft 6a formed on the backward protruding portion of the engine crank shaft, and the first motor 10 is coaxially arranged around the input shaft 28. The first motor 10 is of a synchronous AC permanent magnet type (or a brushless DC motor) and is composed of a stator 10a fixed in a case, and a rotor 10b rotatably supported through a predetermined air gap in the stator.
The power distributing planetary gear 11 is formed of a simple planetary gear arranged coaxially with the input shaft 28, and is composed of a carrier C1 connected to the input shaft 28 for supporting a plurality of planetary pinions P1; a sun gear S1 connected to the rotor 10b; and a ring gear R1 for acting as a power outputting portion. The ring gear R1 is connected to an output shaft 12 extending backward on the axis common with the input shaft 28.
The second motor 40 is formed of a brushless DC motor similar to but larger than the motor 10 and is arranged coaxially with and around the output shaft 12. The second motor 40 is composed of a stator 40a fixed in a case, and a rotor 40b rotatably supported through a predetermined air gap in the stator. Here, the hybrid drive unit 54 is housed in the integral case and is mounted by fixing the front end of the integral case on the rear end face of the engine 6. The output shaft 12 further extends backward from the case and is connected to a differential unit 15 through a flexible coupling 43 and a known propeller shaft 13 (including, as a matter of fact, the universal joint and the center bearing, although not shown) and further from the differential unit through left and right drive shafts 8a and 8b to rear wheels 5a and 5b. 
In the front engine rear wheel drive type automobile 1 having the present hybrid drive unit 54 mounted thereon, the output of the engine 6 is transmitted through the damper unit 9 and the input shaft 28 to the carrier C1 of the power distributing planetary gear 11. At the planetary gear 11, the engine output is distributed and transmitted from the sun gear S1 to the first motor (or generator) 10 and from the ring gear R1 to the output shaft 12. By controlling the first motor 10, the output torque and the rotation are continuously adjusted and outputted to the output shaft 12. When a high torque is required for the starting time or the like, moreover, the second motor (or drive motor) 40 is driven so that the motor torque is transmitted, while assisting the torque of the output shaft 12, to the propeller shaft 13 and further through the differential unit 15 and the left and right drive shafts 8a and 8b to the rear wheels 5a and 5b. 
Here, the second motor 40 employs not only the generated power of the first motor 10 but also, when that power is short, the energy from the battery stored by the first motor 10. The second motor also functions as a regenerator at a braking time.
In the differential unit 15 to which the drive force is transmitted from the engine 6 and/or the second motor 40, on the other hand, hypoid gears may be adopted as a ring gear 26 (as referred to FIG. 2) and a drive pinion 25 (as referred to FIG. 2) meshing with the ring gear 26. This arrangement can be used in order to lower the propeller shaft 13 and accordingly the floor of the compartment, by offsetting the center line of rotation of the ring gear 26 and the center of rotation of the drive pinion 25.